OESTRADIOL-TO-OOCYTE ratio (EOR) may act as a prognostic marker for IVF outcomes in women with polyendocrine metabolic ovarian syndrome (PMOS, formerly known as PCOS).
PMOS is a common endocrine disorder in reproductive-age females and a frequent cause of infertility, characterised by disrupted ovulation and hormonal imbalance.
The findings add nuance to existing evidence that elevated oestradiol during ovarian stimulation can negatively influence assisted reproductive technology (ART) outcomes, potentially through effects on endometrial receptivity and implantation processes.
Lower Ostradiol-to-Oocyte Ratio Linked with Stronger Embryo Outcomes
The oestradiol-to-oocyte ratio in PMOS was evaluated in 276 patients undergoing ART using a retrospective cross-sectional design. Participants were stratified into four EOR categories, alongside subgroup analysis based on luteinising hormone (LH) activity during ovarian stimulation, including no LH, recombinant LH and LH-like activity groups.
The lowest EOR group showed the most favourable embryological performance, with higher numbers of metaphase II oocytes, total embryos, good-quality embryos and frozen embryos. Biochemical and clinical pregnancy rates both showed a declining pattern with increasing EOR, although these differences did not reach statistical significance.
LH Activity During Stimulation Shapes Hormonal Response
LH activity appeared to modify the relationship between hormonal exposure and outcomes. Patients without LH supplementation demonstrated the lowest oestradiol-to-oocyte ratios and achieved the most favourable clinical and embryological results. Multivariable analysis identified absence of LH activity, higher periovulatory follicle counts and lower EOR as independent predictors of improved ART outcomes.
Implications for IVF Strategies in PMOS
The study suggests that the oestradiol-to-oocyte ratio in PMOS may serve as a condition-specific prognostic biomarker in ART. Importantly, the findings indicate that optimal EOR thresholds in PMOS may differ from those reported in broader infertility populations, where intermediate ratios have previously been linked with best outcomes.
This raises the possibility that endocrine context should be considered when interpreting ovarian response biomarkers, particularly in PMOS where ovarian stimulation is often associated with higher oestradiol exposure and an increased risk of ovarian hyperstimulation syndrome.
Study Limitations and Need for Validation
As a retrospective cross-sectional study, the findings are limited by design constraints, including lack of formal power analysis and inability to evaluate PMOS phenotypes. Variability in LH dosing strategies between groups may also have influenced outcomes.
Despite these limitations, the authors highlight this as the first study to evaluate EOR specifically in PMOS using multivariable modelling. They call for prospective validation in larger cohorts, alongside comparative studies across infertility aetiologies, to determine whether EOR can be integrated into clinical IVF protocols.
Reference
Salovic B et al. Estradiol-to-oocyte ratio as a prognostic biomarker of assisted reproductive outcomes in women with polycystic ovary syndrome: The impact of LH activity. Womens Health. 2026;DOI:10.1177/17455057261455286.
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